The present invention relates generally to playing multimedia files over a network and more specifically to the progressive playback of multimedia files as they are downloaded over a network.
Progressive playback is the idea of playing back remote content as it is being downloaded. With this feature a user can select a remote movie and commence watching it before it is fully downloaded. Even with a fast Internet connection, waiting for a movie to fully download can range from minutes to hours depending on the size of the media file. With progressive playback a user only has to wait a couple of seconds before playback can begin.
Current implementations of receiver or player driven progressive playback, while suitable for the short video clips that are dominant in many current applications, are typically limited in the scope and flexibility of the progressive playback they provide. Players typically download files linearly from the beginning to the end. Playback then begins when the player has buffered enough data to provide a likelihood that the media will play without interruption. The buffering requirement can either be a fixed amount suitable for a large percentage of content, or a dynamic amount, where the player infers how much data is required to play the entire content without suffering buffer under-run. Although suitable for playback of short video clips, these methods typically do not support random seeking, trick-play and playback of remotely stored longer content such as feature length movies.
Some systems are implemented with a server driven approach. Examples of server driven approaches include the systems described in U.S. patent application Ser. Nos. 11/323,044, 11/323,062, 11/327,543, and 11/322,604, the disclosure of which is incorporated herein by reference in its entirety. In these systems, the server parses the data file and determines which data to send. Network efficiency and flexibility in playback becomes a much easier task. Standard HTTP web servers however do not typically provide this functionality, and custom web servers providing this functionality often scale poorly when called upon to deliver content simultaneously to a large number of players.
Browser based players often implement receiver driven playback by parsing the video file as it is downloaded linearly. When a long clip is started, it is impossible to seek or fast-forward to a point in the file that has not already been downloaded. Samba (open source software available at http://us2.samba.org/samba/) can be used to give any application access to a remote file as if it were a local file. It tries to minimize the access latency by pre-caching data from the current file position, which can be randomly set. This may be insufficient when trying to perform “trick play” functions (e.g. performing functions such as rewinding, fast forwarding and skipping between scenes that require non-sequential access of media content). The video frames to be delivered to the player in these scenarios can be spaced far apart or require more complex ordering, greatly diminishing the utility of traditional pre-caching methods which are based on assumptions regarding the subsequent video frames to be viewed.